KYT-TERKORCorrosion of low and intermediate level steel waste under in-situ repository conditions

Pauliina Rajala

KYT2022-SAFIR2022 Interim Seminar18.-19.3.2021

TERKORBackground

▪ Steel is studied as possible material included in

maintenance and decommissioning waste

▪ The results support the decisions to be made

concerning the decommissioning phase

• Corrosion rates of the reactor pressure vessels and

other steel components

• Role of corrosion in release of radionuclides to the

environment

…The study also supports the repository of the low and

intermediate level waste produced during operation

09/04/2021 VTT – beyond the obvious 2

Figure: Safety case for Loviisa LILW repository 2018, Public report LO1-T3552-00023

TERKORObjectives

1. Investigate the effect of steel activation on the corrosion rate

in the final repository conditions

2. Determine the role of microbial community on the corrosion

rate and mechanisms of steels in the final repository conditions

3. Utilize deeper characterization of corrosion products and

biofilms to deepen the understanding of microbially-induced

corrosion (MIC) in the final repository conditions.

4. The goal of the project is to expand and compare corrosion data

to cover the activated steels and other repository environments

09/04/2021 VTT – beyond the obvious 3

Long-termlaboratoryexperiment(11 months)

09/04/2021 VTT – beyond the obvious 4

Long-term laboratory experiment(11 months)

▪ Experiment period 11 months

▪ Carbons steel (DC01* AmO ), stainless steels AISI304 (EN 1.4301) and

AISI316(EN 1.4432) and pressure vessel steel 15Kh2MFA from Loviisa

▪ Water from LPVA5, 10°C

▪ Microbial enrichments from LPVA5 water

• Sulphate reducing prokaryotes (SRB), Iron reducing bacteria (IRB),

Iron oxidizing bacteria (IOB)

▪ Real-time monitoring of corrosion rate

▪ Specimens for gravimetric measurements

▪ Specimens for biofilm analyses

▪ Specimens for surface characterization

09/04/2021 VTT – beyond the obvious 5

Comparison of groundwatersfrom differentrepositorysitesChemistry, microbiology and corrosion

09/04/2021 VTT – beyond the obvious 7

Comparison of groundwaters fromdifferent repository sitesChemistry, microbiology and corrosion

▪ Materials: carbon steel and two stainless steels (304, 316)

▪ Water from Olkiluoto KR9, Loviisa LPVA 5, Hanhikivi KR4 and

simulated water

▪ Anoxic conditions

▪ Electrochemical measurements

• OCP

• EIS

• Tafel (carbon steel)

• Cyclic anodic polarization (stainless steels)

▪ Microscopy

09/04/2021 VTT – beyond the obvious 8

09/04/2021 VTT – beyond the obvious

Olkiluoto Hanhikivi Loviisa

304, Olkiluoto

Element/characteristic Unit OlkiluotoKR9

HanhikiviKR4

LoviisaLPVA5

Simulated water

pH 8.73 7.33 7.74 7Alkalinity pH 4.5 mmol/L 3.15 5.41 1.82

CO2 (total) mg/L 138 268 87HCO3

- mg/L 192 330 111Phosphate mg/L <0.040 0.068 <0.040Sulphate mg/L 116 482 566 500Sulphide mg/L 0.147 <0.050 <0.010Chloride mg/L 723 3210 4880 5500Ammonium mg/L 0.179 2.9 1.82Ca (soluble) mg/L 56.8 444 615Mg (soluble) mg/L 30.2 109 276Na (soluble) mg/L 489 1380 2210S mg/L 44.4 140 204Si mg/L 2.28 7.23 4.56TOC mg/L 6.37 10.3 1.33Sulphate/chloride ratio 0.16 0.15 0.12 0.09

Effect of activation on corrosion rateof pressurevessel steel

09/04/2021 VTT – beyond the obvious 10

Effect of activation on corrosion rate of pressure vessel steel

▪ Material: activated and non-activated pressure

vessel steel

▪ Water: LPVA5 and simulated water

▪ Duration 1 year (sampling done 6/2020) and 3

years (2022)

▪ Gravimetric specimens

▪ Specimens for surface characterization (SEM,

EDS)

▪ Specimens for microbial analyses

09/04/2021 VTT – beyond the obvious 11

Activated pressure vessel steel• Main components on the more smooth area

of corrosion product: Fe, O, Si and S and smaller amounts of Ca, C, Cr, Mg, Al

• Main components in the deposits: Ca, C, O

Non activated pressure vessel steel• Main components on the smoother area of

corrosion products: Cu, Fe and S and smalleramounts of Ca, Cr, Zn

• Main components in the crystalline deposits: Ca, O, C

TERKORSummary

▪ Local groundwater conditions (chemical and biological) have

great effect on corrosion tendency and corrosion form of LILW

▪ Laboratory studies targeted to the effects of different microbial

groups on corrosion show that there are differences regarding of

the microbial species composition

▪ Composition of corrosion product on activated steel differed from

non-activated

09/04/2021 VTT – beyond the obvious 13

Publications

Yearly report (in Finnish)

▪ Teräksisten matala- ja keskiaktiivisten jätteiden korroosio loppusijoituksen in-situ olosuhteissa (TERKOR) - Vuosiraportti

2019

Scientific publications

▪ Nuppunen-Puputti M, Kietäväinen R, Purkamo L, Rajala P, Itävaara M, Kukkonen I, Bomberg M. Rock Surface Fungi in

Deep Continental Biosphere—Exploration of Microbial Community Formation with Subsurface In Situ Biofilm Trap.

Microorganisms. 2021; 9(1):64.

▪ P. Rajala, E. Huttunen-Saarivirta, M. Bomberg, L. Carpén. 2019. Corrosion and biofouling tendency of carbon steel in

anoxic groundwater containing Sulphate Reducing Bacteria and Methanogenic Archaea. Corrosion Science 159: 108148.

▪ P. Rajala, M. Raulio, L. Carpen, 2019. Sulphate Reducing Bacteria and Methanogenic Archaea Driving Corrosion of Steel

in Deep Anoxic Ground Water. Corrosion Science and Technology 18 (6): 221-227.

▪ L. Carpen, P. Rajala, E. Isotahdon. 2019. The effect of sulfate reducing bacteria and acetogenic bacteria on the corrosion

of carbon steel in crystalline groundwater, Eurocorr 2019, September 9-13 Seville, Spain.

Presentations

▪ Corrosion induced by deep biosphere microorganisms, Indian institute of Technology Delhi, Seminar series, 12.11.2020

▪ Sammonlahden koulu, 9th grade chemistry class

▪ The effect of sulfate reducing bacteria and acetogenic bacteria on the corrosion of carbon steel in crystalline groundwater,

Eurocorr 2019, September 9-13 Seville, Spain.

09/04/2021 VTT – beyond the obvious 14

09/04/2021 VTT – beyond the obvious 15

The Team

Pauliina Rajala

Leena Carpen

Elisa Isotahdon

Thomas Ohligschläger

Mervi Somervuori

Vilma Ratia-Hanby

Maija Nuppunen-Puputti

Malin Bomberg

Satu Salo

Jarkko Metsäjoki

Taru Lehtikuusi

Tuomo Kinnunen

Seppo Peltonen

Johanna Lukin

Mirva Pyrhönen

KYT-DEMONI